Shaft kiln discharging mechanism



Oct. 14, 1969 J. J. RUIZ 3,472,422

SHAFT KILN DISCHARGING MECHANISM Filed Oct. 26, 1967 I 3 Sheets-Sheet lI I I INVENTOR JOSEPH .1. RUIZ @MMMd KW ATTOI-iNEYS Oct. 14, 1969 J. J.RUIZ SHAFT KILN DISCHARGING MECHANISM 3 Sheets-Sheet 2 Filed Oct. 26,1967 INVENTOR JOSEPH J RUIZ l HHIIHIH ATTORNEYS Oct. 14, 1969 J. J. RuizSHAFT KILN DISCHARGING MECHANISM 3 Sheets-Sheet 3 Filed Oct. 26, 1967INVENTOR JOSEPH J. RU/Z ,zrzalg pw zz a KM ATTOR NE YE United StatesPatent O 3,472,422 SHAFT KILN DISCHARGING MECHANISM Joseph J. Ruiz,Cleveland, Ohio, assignor to Basic Incorporated, Cleveland, Ohio, acorporation of Ohio Filed Oct. 26, 1967, Ser. No. 678,029

Int. Cl. B67d /02 US. Cl. 222-1 23 Claims ABSTRACT OF THE DISCLOSURE Ashaft kiln having inlet and outlet means and means to apply heat to thekiln and material passing therethrough. The kiln has a rectangularoutlet at the discharge end and a discharge mechanism positionedadjacent the outlet to receive material therefrom. The dischargemechanism is in the form of a prism which reciprocates transversely ofthe outlet and receives the material as it is discharged from the kiln.

DISCLOSURE This invention relates generally as indicated to a shaft kilnand to a discharging mechanism for such kiln, and more particularly tosuch a kiln and discharging mechanism whereby uniform downward movementof material passing through the kiln is achieved.

Shaft or vertical kilns of the type to which the present inventionrelates have generally been known for many years for calcination,sintering or other heat treatment of granular materials such aslimestone, magnesite, alumine. and the like. Shaft kilns are usuallyvertical kilns in which a'charge of material to be treated passesdownwardly through the open top of the kiln in countercurrent flow to anupwardly moving stream of hot gas. The temperature of the upwardlymoving gases, of course, depends upon the type of material being treatedas well as the desired heat treatment.

One problem which is frequently encountered in shaft kilns is that ofachieving uniform downward movement of the material at all points withinthe cross-section of the kiln. The inability to achieve such uniformmovement may result in non-uniform heating of the material and unevenprocessing, which in turn can cause coalescence of the granular materialand even clogging of the kiln when such condition becomes exaggerated.

Another problem which is encountered in shaft kilns is that of achievinguniform distribution of combustion of fuel or penetration of heatthrough the entire kiln cross-section. In attempting to overcome thisproblem, kilns have been designed of oval cross-section to reduce thedistance which the heating gas must travel in order to penetrate thegranular material passing through the kiln. Kilns of oval cross-section,although facilitating penetration of the heating gas, do not readilypermit uniform movement of the granular material through the kiln oruniform discharge from the kiln outlet.

To overcome the discharge problem, variou discharge mechanisms have beenprovided in association with the kiln outlet. One such mechanism is amechanical conveyor illustrated in US. Patent 3,094,016. Another suchdevice is a reciprocating drag bar mechanism shown in US. Patent3,165,304. These devices are not entirely satisfactory, however, andwith the drag bar mechanism particularly, it has been found that someareas of the granular material are hotter than others, which likewisetends to produce uneven processing as well as coalescence of thematerial.

It is an object of the present invention, therefore, to provide a shaftkiln with a discharge mechanism whereby uniform downward movement ofgranular material through such kiln is achieved.

Another object of this invention is the provision of a dischargemechanism for shaft kilns and the like whereby coalescence of granularmaterial within such kiln will be avoided.

It is a further object of this invention to provide such a dischargemechanism whereby a uniform discharge of treated material from the kilnwill be obtained.

Still a further object of this invention is the provision of a dischargemechanism for shaft kilns which includes means to distribute and coolmaterial as it is received from the outlet of a kiln.

Another object of this invention is the provision of a process for theuniform movement and discharge of granular solids from a vertical kiln.

Other objects, features and advantages of this invention will becomeapparent to those skilled in the art after a reading of the followingmore detailed description.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principle of the invention may beemployed.

In said annexed drawings:

FIG. 1 is a fragmentary cross-section view of the outlet of the kiln andthe discharge mechanism associated therewith;

FIG. 2 is a fragmentary cross-section view of such kiln taken on line2-2 of FIG. 1;

FIG. 3 is a plan view in section taken on line 33 of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3; and

FIG. 5 is an enlarged fragmentary view of the stepped prism dischargemechanism of this invention.

Referring to the drawings, a shaft furnace or kiln is designatedgenerally by the numeral 1 and includes an upper inlet (not shown) intowhich the granular material to be treated is introduced. Such kiln alsoincludes rectangular outlet 2 and a reciprocably movable dischargemechanism designated generally by numeral 3 positioned adjacent theoutlet to receive material therefrom. The kiln also, of course, includesa refractory lining 4 on the interior wall and means to apply heat (notillustrated) to the material moving therethrough. The refractory lininggradually slopes inwardly as shown at 4A to accommodate rectangularoutlet 2.

The discharge mechanism includes a movable supporting frame 5, dischargeplates 6 and a prism 7 of trapezoidal configuration as shown mostclearly in FIGS. 2 and 5, which extends to a width substantially equalto the kiln outlet 2. As shown in FIG. 2, the discharge plates extendbeyond the kiln outlet sufiiciently to permit the granular solids toform a pile at the natural angle of repose. The discharge mechanism alsoincludes a lower frame 3 which has a conduit 9 and tributory conduits 10and 11 through which air passes for cooling. As shown more clearly inFIG. 3, the surface of frame 8 has a plurality of apertures 12distributed thereabout through which air passes at high velocityproducing air jets to cool the discharge mechanism and to assist incooling the granular material.

The discharge mechanism is designed for reciprocable movementtransversely of the outlet of the kiln, and this is preferably achievedby a mechanical drive arrangement, such as that illustrated in FIGS. 1,2 and 3. As thus illustrated, the drive means includes a pair ofeccentrics 15 and 16 which rotate toward center in opposite directionsto lessen the thrust on centering roll 17, which is displaced betweenguide blocks 18 and 19 which are mounted on the movable frame 5. Themovable assembly (frame 5, discharge plates 6 and prism 7) is supportedby a plurality of rollers 20, 21, 22 and 23 which are mounted on lowerstationary frame 8. It will, of course, be appreciated that any numberof such rolls may be provided. The eccentrics are connected through gearreducers 24 and 25 to a main drive motor 26 by a single common shaft 27which operates through a pulley connection.

The construction of a preferred form of the prism is shown most clearlyin FIG. as a stepped prism which comprises a plurality of steps 30, 31,32, 33 and 34 and a top tread or substantially fiat surface 35. Thelongitudinally extending bars which form the stepped prism are spaced asshown to provide a clearance between adjacent bars for the passage ofcooling air. The tread 35 has bars 36 and 37 disposed at an anglethereto substantially equal to the angle of repose to facilitatemovement of the material and to provide openings for air flow to thecenter of the kiln. The bar which extend longitudinally of the prism aresupported by a plurality of spaced plates 38 (see also FIG. 1). Becauseof the stepped prism construction of the discharge mechanism, thegranular material will be withdrawn from the kiln at a uniform ratethroughout the cross-section.

Although the stepped prism is a preferred form, the prism may beprovided without the steps in which case bars 36 and 37 would beextended and in contact with discharge plates 6. It is to be understood,of course, that such embodiment is within the confines of the presentinvention.

Because of the greater heat of the granular material as it is receivedfrom the kiln outlet, the top tread 35 of the stepped prism ispreferably stainless steel, AISI Specification 309. The bars forming thetreads of the steps 30, 31, 32, 33 and 34 are preferably steel such asASTM A-514, but may also be of a suitable ceramic material if desired.The steps are preferably approximately 1 /2 inches apart in tread andthe step height should be approximately twice the average particle sizeof the granular material being treated, since the particles must fitinto the steps to move from one step to another.

The stepped prism also includes end plates 40 and 41 to prevent granularmaterial from being removed at the ends thereof. These plates are angledoutwardly toward the periphery of the prism as shown in FIG. 3 at 42 inorder to overcome the friction of the granular material against theplates and to permit an even flow of material.

In order to provide the most efficient discharge of material and henceprevent coalescence of material in the kiln, it has been found that thedischarge mechanism should preferably be designed so that it willreciprocate a maximum transverse movement of approximately twice thetread width of the steps, which in the preferred form is approximately 3inches.

As can be readily appreciated from FIG. 2, the material is uniformlywithdrawn from the kiln and received by the discharge mechanism in aplurality of zones controlled by the bars of the stepped prism. Thegranular solids will accumulate on the discharge plates 6 in a pile,shown by the phantom line, at an angle substantially equal to thenatural angle of repose and will be discharged laterally from the platesby the reciprocating movement of the discharge mechanism, falling intohopper 45 and into outlet 46. Outlet 46 is of a standard commerciallyavailable type for removal of the granular material from the pressurizedhopper 45 while preventing the discharge of air an dhence will not bedescribed in further detail.

Other modes of applying the principle of the invention may be employed,change being made as regards the de tails described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a vertical kiln including an upper inlet and a bottom outlet andmeans to apply heat to said kiln and to a granular material as suchmaterial passes therethrough, the improvement comprising a rectangularoutlet on said kiln for the discharge of granular material and adischarge mechanism positioned adjacent said outlet to receive materialtherefrom, said discharge mechanism comprising a reciprocating prism ofa width substantially equal to the width of the outlet of said kiln,means adjacent said prism to confine said material within said width,and means associated with said discharge mechanism to reciprocably movesaid mechanism transversely of said outlet to move uniformly suchgranular material through said kiln.

2. The kiln of claim 1 wherein said discharge mechanism includes meansto cool the same during operation of said kiln.

3. The kiln of claim 2 in which said discharge mechanism comprises asupporting frame positioned beneath said discharge mechanism havingconduit means connected thereto and a plurality of apertures in thesurface thereof, whereby air may flow through said conduit and throughsaid apertures to effect cooling of said discharge mechanism.

4. The kiln of claim 1 in which said means to confine said materialcomprises plates on the ends of said discharge mechanism.

5. The kiln of claim 4 in which said end plates are angled outwardlytoward the periphery of said mechanism whereby friction of the granularmaterial against said plates is overcome and an even flow of material ispermitted.

6. In a vertical kiln including an upper inlet and a bottom outlet andmeans to apply heat to said kiln and to a granular material passingtherethrough, the improvement comprising a rectangular outlet on saidkiln for the discharge of granular material and a discharge mechanismpositioned adjacent said outlet to receive such material therefrom, saiddischarge mechanism comprising a reciprocating stepped prism of a widthsubstantially equal to the width of the outlet of said kiln, dischargeplates extending therefrom, and means adjacent said prism to confinesaid material within said width and means associated with said dischargemechanism to reciprocably move said mechanism transversely of saidoutlet to move uniformly such granular material through said kiln.

7. The kiln of claim 6 in which said stepped prism is of a trapezoidalconfiguration, and said discharge plates extend beyond said kiln outletsufficient to permit such granular material to form a pile at thenatural angle of repose.

8. The kiln of claim 7 in which said discharge mechanism includes amovable supporting frame for said stepped prism and discharge plates anda stationary supporting frame positioned beneath said movable framehavinr, conduit means connected thereto and a plurality of apertures inthe surface thereof whereby air may flow through said conduit andthrough said apertures to effect cooling of said discharge mechanism.

9. The kiln of claim 6 in which said discharge mechanism is capable of amaximum reciprocable movement of approximately twice the width of thetreads.

10. The kiln of claim 6 in which said discharge mechanism has mechanicaldrive means associated therewith to effect such reciprocable movement.

11. The kiln of claim 6 in which the steps of said stepped prismdischarge mechanism are approximately 1 /2 inches apart in tread.

12. The kiln of claim 6 in which the step height of said stepped prismdischarge mechanism is approximately twice the average particle size ofthe granular material passing through said kiln.

13. The kiln of claim 6 in which the treads of said stepped prismdischarge mechanism are steel.

14. In a vertical kiln including an upper inlet and a bottom outlet andmeans to apply heat to said kiln and to a granular material passingtherethrough, the improvement comprising a rectangular outlet on saidkiln for the discharge of granular material and a discharge mechanismpositioned adjacent said outlet to receive such material therefrom, suchdischarge mechanism comprising a reciprocating stepped prism anddischarge plates extending therefrom, and means associated with saiddischarge mechanism to reciprocably move said mechanism transversely ofsaid outlet, the steps of said stepped prism being spaced to provide aclearance between adjacent steps for the passage of cooling air throughsaid prism.

15. In a vertical kiln including an upper inlet and a bottom outlet andmeans to apply heat to said kiln and to a granular material passingtherethrough, the improvement comprising a rectangular outlet on saidkiln for the discharge of granular material and a discharge mechanismpositioned adjacent said outlet to receive such material therefrom, suchdischarge mechanism comprising a reciprocating stepped prism anddischarge plates extending therefrom, and means associated with saiddischarge mechanism to reciprocably move said mechanism transversely ofsaid outlet, the top tread of said stepped prism having bars disposed atan angle thereto substantially equal to the angle of repose tofacilitate movement of granular material and to provide openings for airflow to the center of said kiln.

16. The kiln of claim 8 in which said means to confine said materialcomprises plates on the ends of said discharge mechanism.

17. The kiln of claim 16 in which said end plates are angled outwardlytoward the periphery of said mechanism whereby friction of the granularmaterial against said plates is overcome and an even flow of material ispermitted.

18. A discharge mechanism for use with shaft kilns and the like having avertical discharge outlet of Substantial width comprising areciprocating prism of a width sufficient to extend across the width ofsaid outlet of such a kiln, means adjacent said prism to confine thematerial within said width and means associated with said dischargemechanism to reciprocably move said mechanism transversely of the outletof such a kiln.

19. The discharge mechanism of claim. 18 in which said reciprocatingprism is a stepped prism of a trapezoidal configuration and includesdischarge plates extending substantially laterally therefrom.

20. The discharge mechanism of claim 19 including a movable supportingframe for said prism and discharge plates and a stationary supportingframe positioned beneath said movable frame having conduit meansconnected thereto and a plurality of apertures in the surface thereof,whereby air may flow through said conduit and through said apertures toeffect cooling of said discharge mechanism.

21. The discharge mechanism of claim 20 including plates on the endsthereof to prevent granular material from being removed from saidmechanism at such ends.

22. The discharge mechanism of claim 21 in which said end plates areangled outwardly toward the periphery of said mechanism whereby frictionof granular material against the said plate is overcome and an even flowof such material is permitted.

23. In a process of heat treating granular solids in a vertical kilnhaving a vertical discharge outlet of substantial width wherein suchsolids are moved downwardly through such kiln countercurrently to aheating gas, the improvement comprising uniformly moving such solidsthrough such kiln and withdrawing such solids therefrom in a pluralityof zones by reciprocably moving a stepped prism discharge mechanismtransversly of said outlet of such kiln while confining such solidswithin the width of said outlet.

References Cited UNITED STATES PATENTS 2,300,860 1l/l942 Azbe 222-409 X2,577,315 12/1951 Ellerbeck 222-409 X 3,104,038 9/1963 De Koning 222-409FOREIGN PATENTS 1,116,700 11/1961 Germany.

ROBERT B. REEVES, Primary Examiner H. S. LANE, Assistant Examiner US.Cl. X.R. 222--146, 409

